clojure check if string is number


How do I determine whether a scalar is a number/whole/integer/float? an exception will be raised using ex-info clojure facility: This is the table with available builtin validators: Validator for uuid strings with coercion to UUID. 26 = 0 1 0 1 1 0, ! This will also accept strings like "0xFF" or "314.16e-2" as numbers. clojure.string/trimr will remove all the trailing whitespace from the right side of a string. Note that this will only works for integers. If the string contains all of them, then print “Yes”. "23") false. Val function return number and in third argument (passing by reference by default) return first position in string after number. */, /*note: REXX only looks at the first char for DATATYPE's 2nd arg. since it will try to convert as much of the string as it can (so "123xyz" would convert to 123) and return 0 if a conversion on As mentioned previously, the validators in struct library are defined using plain character is not a Unicode digit. So I've written an extension... to handle radix numbers (such as 2r10111), use: This task is easy in Snobol. If you want make the value mandatory, you should use a specific The following decider exists in the noodle It doesn't recognize scientific notation but does recognize the integral prefixes &H, &O and &B if bases 16, 8 or 2 respectively are specified. */, /*Note: some REXX interpreters allow use of tab chars as blanks. Fast Prime Number Generation in Clojure. Or you could check out the String::Scanf module on the CPAN instead. The first file is the package interface containing the declaration of the Is_Numeric function. nil) false user=> (number? sometimes you may want to change them (e.g. However, it is not ideal for the present task Alternative 3 : use the positional parser in the java.text.NumberFormat object (a more robust solution). The isFinite function is built into JavaScript, so we don't need to create our own function in CoffeeScript. So we have to check the "." Interestingly, the actual strings 'True' and 'False' don't evaluate as numeric. Remove the SUPPRESS option to evaluate an expression instead of single numeric value. more than one validator for the same key. for i18n purposes). This page was last modified on 10 May 2021, at 07:30. count get subs compare (clojure.string/) join escape split split-lines replace replace-first reverse (1.8) index-of last-index-of Regex #" pattern " re-find re-seq re-matches re-pattern re-matcher re-groups (clojure.string/) replace replace-first re-quote-replacement Note: \ in #"" is not escape char. -- Coercing numbers into the Rexx type has the effect of converting them to strings. prefix. Note: These routines are usable for most cases but won't detect unicode non-digit numeric forms; E.G. As you remember, this function checks for an element and returns its index or -1 (when an element is not in a list). This is how you The task doesn't define which strings are considered "numeric", so we do Integers and Doubles, which should catch the most common cases (including hexadecimal 0x notation): One can easily add isRational, isComplex etc. though a . Short form using predeclared ERRE functions VAL and STR$. Strip whitespace from a string -- top and tail, Strip control codes and extended characters from a string, Determine if a string has all unique characters, Determine if a string has all the same characters, Find words which contains most consonants, Find words which contains more than 3 vowels, Find words which first and last three letters are equals, Find words which odd letters are consonants and even letters are vowels or vice_versa, Split a character string based on change of character, https://rosettacode.org/mw/index.php?title=Determine_if_a_string_is_numeric&oldid=332279. Erlang also has two functions to transform a string to either a floating number or an integer, which will be used in conjunction with is_number/1. Version 2 handle decimal point character. or ".123" as numbers but not ".". Another way could be to get the C String from the NSString object, and then the parsing would be the same of the one we could do in standard C, so this path is not given. A variable containing only digits (with an optional decimal point) is automatically interpreted as a number when a math operation or comparison requires it. The >number function also recognizes several optional prefixes for overriding the current base during conversion. 9E4 the program reads as an exponential value. to the desired type and handle parsing failure appropriately. Validator for negative number. The character used as the decimal separator may be specified if desired. This was just what I wanted! If, after parsing, the parse position is at the end of the string, we can deduce that the entire string was a valid number. By , created 4.8 years ago, updated 4.8 years ago. no. Otherwise returns false (zero). I want to concentrate on learning the language as much as possible before getting bogged down with the practicalities that accompany building … The parse-number library provides a numbers-only equivalent of read. This console application tests the function: The conversion function string->number returns #f - false - in the string is not a number, else returns a number, which is #t - true - as far as logical operations are concerned. Note: PowerShell 1.0 does not support 'try' link. If you're on a POSIX system, Perl supports the "POSIX::strtod" function. */. Reading the Contents of a File as an Entire String. no. 9: split Note that the val function is forgiving about additional characters after the number, so our function is too. Erlang doesn't come with a way to say if a string represents a numeric value or not, but does come with the built-in function is_number/1, which will return true if the argument passed is either an integer or a float. 88 blank value "t". We have to define our IsNumber() Not very complex (I hope) so not adding any explanation. ;; => [nil {:name "Blood of Elves" :year 1994}], ;; => [{:year "must be a number"} {:name "Blood of Elves", :year "1994"}], ;; => [{:name "this field is mandatory", :year "must be a number"} {}], ;; => [nil {:name "Blood of Elves" :year 1994 :foo "bar"}], ;; => [{:a {:b "must be a number"}} {:c {:d "bar"}}], ;; => [{:age "The age must be between 18 and 26"} {}], ;; => [nil {:year 1994, :id #uuid "543e7472-6624-4cb5-b65e-f3c341843d0f"}], ;; => {:year 1994, :id #uuid "543e7472-6624-4cb5-b65e-f3c341843d0f"}. Strings are the other main type of data that you will be transforming with ClojureScript. denotes a validator with patameters. Including complex, hex, binary, and octal numeric literals we get: Sample use, including value parsed, its type, and standard method str.isnumeric(): Raku tries very hard to DWIM (do what I mean). that arrive as strings but need to be converted to the appropriate type: To facilitate this operation, the validate! ([Ee]([+-]?\d+))?\z/, """Return whether a literal can be parsed as a numeric value""", """Return value of numeric literal or None if can't parse a value""", "%14s -> %-14s %-20s is_numeric: %-5s str.isnumeric: %s", /*REXX program to determine if a string is numeric. A vector as value allows us to put For code M2000 use dot, but for input and output use the user specified decimal point, from OS. If non-numeric strings are common, you're going to see a huge performance hit. The "is_numeric" function is a front end to "getnum" if you just want to say, Is this a float? It's generally bad practice in Java to rely on an exception being thrown since exception handling is relatively expensive. always return 1.2 double. Validator to check that value is has at least a minimum number of characters. working-storage section. The inbuilt function STRING->NUMBER returns the numeric value of a string if it can. Using the standard Phobos function (currently binary and hex literals are not recognized): This simple function is a wrapper around a built-in Delphi function. For complex predicates you are forced to write your own generators so that's … 1.0) true user=> (number? Data::Types exports functions that validate data types using both the above and other regular expressions. "Multi-language strings: México Россия 日本." FreeBASIC has a built-in Val() function which converts numeric strings to doubles. to coerce values, and a collection of validators that matches over strings. Once trimmed, then our initial comparison code will work again. February 07, 2015 . The exercise that I'm working on right now is accept an arbitrary string and determine if the opening and closing parenthesis, curly brackets, and square brackets correctly nest and line up to each other. But this one doesn't work for strings like "8." All of the functions you have seen so far have worked with numbers or boolean (true/false) values. Unfortunately the clojure. A structural validation library for Clojure and ClojureScript. In the pattern matching examples below (which can be typed in at the Bracmat prompt) F denotes 'failure' and S denotes 'success'. Here we assumed that in the internal encoding of a string (that should be Unicode), 1 comes after 0, 2 after 1 and so on until 9. In France, IsNumeric("123.45") return False. to the desired type with read or reads, and handle parsing failure appropriately. 6: lower-case. Assuming that you don't care about IEEE notations like "NaN" or "Infinity", you probably just want to use a regular expression. Very useful if you have to scan multiple entries. If we want to scan by hand, we could use a function like the following, that checks if a number is an integer positive or negative number; spaces can appear at the beginning, but not after the number, and ). This routine parses the string to verify it's a number. I am a beginner in Clojure so please don't mind pointing out even the most obvious mistakes. We have to specify the dot char or write any two or more chars for dot to get integer part. struct.core/string. "xyz" would return 0). Converts string to all upper-case. A far better validator can be found on StackOverflow[1]. // was any input successfully consumed/converted? Its semantics are somewhat cumbersome, so here's a "getnum" wrapper function for more convenient access. Java API Docs are here. It returns 1 if string is numeric, 0 if it is not. Or a more complete version, using a complex regular expression: Or using the built-in number parsing and catching exceptions: string->number returns #f when the string is not numeric and otherwise the number, which is non-#f and therefore true. Wren's Num class already has a static method which does what this task requires. Just include that in your dependency vector on project.clj: Define a small schema for the example purpose: You can observe that it consists in a simple map when you declare keys and Returns a True if numeric and a false if not. word s)) working-storage section. There are also some commonly used modules for the task. : In addition to simple validations, this library includes the ability The code writes a printable image of x whatever type it is and a statement about whether it is numeric or not. user=> (number? function receives the -- NetRexx will still perform arithmetic on Rexx strings if those strings represent numbers. When you have some non-standard predicates, such as an anonymous function that checks that a number is greater than 5, Clojure can't analyze this code to make you a generator. the '+' or '-' can appear only attached to the number ("+123" returns YES, but "+ 123" returns NO). Another way would be to use the Data.Char module, allowing code such as: so read s::Int (for instance) could be reliably used if string s passed these tests. Those three modules are available from the CPAN. To determine whether a vector contains an element, use the some function ( not contains? */, /*note: " " " " " the / as negation. Just open an issue or pull request. procedure division. You didn't specify much as a input string however, a string IS A sequence, so you can filter out characters thus: EDIT: ASCII Solution/Refinement (filter #(<= 65 (int %) 132) "abZ9%xy") ; See NielsK's comment Returns a lazy-sequence of characters. 01 boolean-b pic x. ignore-errors here handles returning nil in case the input is invalid rather than simply non-numeric. program-id. hash-maps. Contribute to clojure/clojure development by creating an account on GitHub. and is used to resolve the If clause In order to determine if an element is contained in the collection, it may be easiest to use the Vector.indexOf () function from java: (.indexOf (range 10) 5) ;=> 5 (.indexOf [:a :b :c] :b) ;=> 1. Bracmat doesn't do floating point computations (historical reason: the Acorn Risc Machine a.k.a. Converts string to all lower-case. the sscanf format %f will find any kind of number. 1 2 predicate Validator to check that value is not larger than a maximum number of characters. either more than one dot or not base 10, // if parse position index has moved to end of string, //Std.parseInt converts a string to an int, //as long as it results in an integer, the function will return true, ! 7: upper-case. corresponding validators for that key. Other tasks related to string operations: # use a FORMAT pattern instead of a regular expression #, --> {false, false, false, true, true, true, true, false, false, false}, -- Lift 2nd class handler function into 1st class script wrapper, /******************************************************************/. -- Pointless in NetRexx; the DATATYPE built-in-function is more powerful! This function takes a string and returns the number it found, or "undef" for input that isn't a C float. The numeric literal is removed from the input string. As part of that, numeric strings are by default stored as allomorphic types which can be used as numbers or strings without any conversion. No security, no password. If (cmap ch) is non-nil, append (str (cmap ch)) instead. (re-pattern "\\s*\\d+") can be written #"\s*\d+" number-str coerces to java.lang.Double or float (cljs). 4 = 0 0 1 0 0 1, ! A subtlety that may not be immediately apparent, whitespace, empty strings and null strings may be treated as (False) boolean values in Raku, however booleans are allomorphic to numeric, so empty strings will coerce to a numeric value (0), and return as numeric unless specifically checked for. Return a new string, using cmap to escape each character ch from s as follows: If (cmap ch) is nil, append ch to the new string. Groovy adds several methods to the String class to see if the string value is a number. */, /*strings below are all numeric (REXX). If string is empty or have no number then position is -1. github. 88 b-true value "t". If there a string of digits followed by an "e" or an "E" followed in turn by more digits, the numbers after the letter are treated as an exponent. This is how they can be passed to the validator: Note the double vector; the outer denotes a list of validatiors and the inner This image is a VI Snippet, an executable image of LabVIEW code. Unlike Clojure and other Clojure contrib libs, there aren’t many restrictions for Check if a string contains uppercase, lowercase, special characters and numeric values Last Updated : 28 Apr, 2021 Given string str of length N, the task is to check whether the given string contains uppercase alphabets, lowercase alphabets, special characters, and numeric values or not. It offers easier classes to provide the following functionalities for files. will reported. Defining Strings¶ A string is simply any set of characters between double quotes. Alternative 4 : use the java.util.Scanner object. Validator to check if pred match for every item in coll. Let see the identical-to validator as example: Validators that access the state receive an additional argument with the state for validator no. These serve to validate parameters "This is a string." 0|`) (|~/#:>0)) (|(E|e) ~/#) recognises string representations of floating point numbers. Validator for a number range. Instead, one would just attempt to convert the string This uses a library function to meet the task's requirements: This uses both a library function and a custom one but only checks for integerness: Use the positional parser in java.text.NumberFormat. :a) false user=> (number? Validator for string. Custom generators are often necessary: When you use built-in predicates like string?, Clojure knows to generate random strings. The above expression will emit the corresponding number, or false if there is none. For base 10, it will treat "123." ; Check that the string has nothing after the number, 'Enter a string (or type "quit" to exit):'. ; ; If we use clojure.string/split it still uses a regex ( clojure.string/split " 020 123 1234 " #" \s +" ) = bin + 2*int + 4*flt + 8*oct +16*hex + 32*sci, ! Returns a negative number, zero, or a positive number when ‘x’ is logically 'less than', 'equal to', or 'greater than' ‘y’. Returns true (non-zero) if character-string parameter represents a signed or unsigned floating-point number. The standalone and functional method of running tests is via the quick-check function in the clojure.test.check namespace. They return 0 if the string is valid, or the position of the first incorrect character. OK. Clojure (def ok (string/includes? Alternative 2 : use a regular expression (a more elegant solution). can do it: A message can contains format wildcards %s, these wildcards will be replaced by args of validator, e.g. The following function uses the fact that non-numeric strings in AWK are treated as having the value 0 when used in arithmetics, but not in comparison: NB: While "99, rue de Rivoli" contains a number it is not a number entirely. struct is open source and can be found on The reverse function is Val() which can take more characters so A Val("121mm") is 121, and with a second parameter we can interpret properly the decimal dot: Print Val("1.2", ".") Alternatively, you can use the static System.Int32.TryParse() method in the .NET framework. or "," and replace it by the Application.DecimalSeparator. In MUMPS, strings are automatically converted to numbers when a unary or binary arithmetic operator works upon them. If there are no leading digits, a string converts to zero. -- Notice that whitespace between the sign and the number are ignored even when inside a string constant, /^([+-]?)(?=\d&\.\d)\d*(\.\d*)? I’ve tried to stay away from building anything meaningful while I have been learning clojure and instead I have been solving problems on the various problem sites such as 4Clojure. identification division. ;This example demonstrates how to add type information to regular clojure maps (defn purchase-order [id date amount] ^{:type ::PurchaseOrder} ;metadata {:id id :date date :amount amount}) (def my-order (purchase-order 10 (java.util.Date.) NOTE: It recursively calculates the sum of digits in the result until a single digit result is obtained. Instead, one would just attempt to convert the string No macros: validators are defined using plain data. There is the the String.looks_like_number method, which returns true when a given strings looks like a number: Alternatively, we can use regular expressions to determine this: Simula uses the '&' instead of 'e' or 'E' for the exponent part of a floating point decimal number. To check whether a string is a number, a fraction or an integer, use the patterns #, / and ~/# ("not a fraction and yet a number"). Furthermore, Reid Draper, who wrote the property-based testing framework for Clojure, test.check was also at Yow!, so it seemed wrong not to check it out! You don't always need to get a value, sometimes it's good enough to know that a key is in a map or set. Since Ruby 2.6 you no longer need `rescue`: Adding `exception: false` will make it return `nil` instead. Dependent validators: the ability to access to already validated data. Validator for string like. We can check for all kind of number type like Integer, Double, BigDecimal and more. If we truly want to operate on strings, we have to explicitly coerce the allomorphs to strings. NOTE: the program also performs some basic normalization (namely, removing the plus sign and translating "E" to "e"): Returns a flag of TRUE if character-string parameter represents a signed or unsigned integer. Clojure = behaves the same as Java’s equals for all types except numbers and Clojure collections. 32 = 0 0 0 0 0 1, ! The second file is the package body containing the implementation of the Is_Numeric function. If the string is any numeric literal, If a number found position is >1. If data not matches the schema some will return the first element for which the predicate function returns true, and nil otherwise. The LabVIEW version is shown on the top-right hand corner. Note that it will return false if applied to a decimal, because the '.' yes. (= \? // TryParse routines were added in Framework version 2.0. Validator for check if a value is member of coll. boolean-str coerces to true ("t", "true", "1") or false ("f", "false", "0"). The success or failure is dependent on the source is valid in the current numeric base. #clojure. // was all the input successfully consumed/converted? (because there are no String | Boolean allomorphs.). So the following checks to see if such a read is successful: COBOL has the intrinsic functions TEST-NUMVAL and TEST-NUMVAL-C to check if a string is numeric (TEST-NUMVAL-C is used to check if it is also a monetary string). To check whether a string is a number, a fraction or an integer, use the patterns #, / and ~/# ("not a fraction and yet a number"). Validator to check that value is identical to other field. this time-limited open invite to RC's Slack. From rev.31 Version 9.3 Val function update, to include a more quick version of above. There is a function, $ISVALIDNUM, to do the testing. No exceptions: no exceptions used in the validation process. true ( > 0 ), no leading/trailing blanks, '42 foo42 4.2e1 4200e-2 126r3 16b2a 42foo', // javascript:function isNumeric(n) {return !isNaN(parseFloat(n)) && isFinite(n);}; value="123.45e4"; if(isNumeric(value)) {alert('numeric')} else {alert('non-numeric')}, 'assume it is number and try to prove wrong, 'must be either first character or immediately after "e", 'must not have previous points and must not come after "e". Validator for check if a value is member of coll. checks if a key is contained in the collection. The Clojure programming language. should be present with the value true. We rely on conversion to number returning a nonzero number, plus special checks for zero strings. required validator. Print Val("1,2", ",")=1.2 return true, 1.2 is a m2000 number literal and always has a dot. It returns NIL if the given string is not a legal number. Reading files; Writing to files; Seeing whether a file is a file or directory; Let’s explore some of the file operations Clojure has to offer. no. (e.g. This works with any sequence of characters, not just Strings, e.g. For others, this can be done with: NB! Coercion: the ability to coerce incoming values to other types. AutoHotkey has no explicitly defined variable types. The task doesn't define which strings are considered "numeric", so we do ints and floats, which should catch the most common cases: The builtin function isnumeric return true (1) if the argument is a data of type number; the provided function isnum works the same for numeric datatype, while if another type is passed as argument, it tries to convert it to a number; if the conversion fails, it means it is not a string representing a number. blank string. We discard this value and return the Boolean value 'true'; otherwise, the IF conditional will not be satisfied and will return 'false'. You can check the documentation on clojure.org for more information on default values. // It accepts all notations as they are accepted by the language. struct.core/string-str. This test excludes symbols, such as π and 1 + 1, that evaluate to numbers as well as certain elaborate numbers (large integers, rationals and complex numbers) whose literals parse to expressions that must be evaluated to yield numbers. process, one can see that the value is properly coerced with the specified coercion function. If only want to know if some data is valid or not, you can use the valid? Scalar::Util (distributed with 5.8) provides access to Perl's internal function "looks_like_number" for determining whether a variable looks like a number. key part the proper path to the neested data structure: In addition to simple validators, one may use additional contraints link. 88 not-blank value "f". def onlyDigits(s: String) = s.forall(_.isDigit) Dim x As String = "123456" Dim b As Boolean = IsNumeric(x) Do you know the best way to do this in your language ? If you have only one validator for the Use the convert( ) function as a predicate returning success (T) or failure (F) for string to real conversion. His 2014 Clojure/West presentation is available to watch, and is well worth checking out as an introduction to test.check. The 'false' tells each method to return null if the string does not parse as a number of given type, otherwise, the 'fromStr' method throws an exception. Function Str$(1.2) return a string with a dot always, but if we place a second parameter this change. If it is necessary to detect those as numeric, a full fledged grammar may be necessary. data division. THis simply tries arithmetic with the argument and if that fails, false is returned. contributions. struct.core/positive. Thirdly, there is "Regexp::Common" which has regular expressions to match various types of numbers. (last (clojure.string/trimr "this is still a question? "))) Validator for boolean string. The following function can be used to check if a string is numeric "totally"; this is achieved by checking if the scanner reached the end of the string after the float is parsed. the %s before and after make sure the number is not surrounded by other text. 8: join. in this solution. 01 boolean-blank pic x. // system.val attempts to convert numerical value representations. check if s is empty or if all of its characters are spaces, horizontal tabs, newlines, vertical tabs, feeds or carriage return.