OpenSCAD User Manual/String Functions

From Wikibooks, open books for an open world
Jump to navigation Jump to search

str[edit | edit source]

Convert all arguments to strings and concatenate.

Usage examples:

echo ("This is ",number,3," and that's it.");
echo (str("This is ",number,3," and that's it."));


ECHO: "This is ", 2, 3, " and that's it."
ECHO: "This is 23 and that's it."

This can be used for simple conversion of numbers to strings

s = str(n); 

chr[edit | edit source]

[Note: Requires version 2015.03]

Convert numbers to a string containing character with the corresponding code. OpenSCAD uses Unicode, so the number is interpreted as Unicode code point. Numbers outside the valid code point range produce an empty string.


Convert one code point to a string of length 1 (number of bytes depending on UTF-8 encoding) if the code point is valid.
Convert all code points given in the argument vector to a string.
Convert all code points produced by the range argument to a string.


echo(chr(65), chr(97));      // ECHO: "A", "a"
echo(chr(65, 97));           // ECHO: "Aa"
echo(chr([66, 98]));         // ECHO: "Bb"
echo(chr([97 : 2 : 102]));   // ECHO: "ace"
echo(chr(-3));               // ECHO: ""
echo(chr(9786), chr(9788));  // ECHO: "☺", "☼"
echo(len(chr(9788)));        // ECHO: 1

Note: When used with echo() the output to the console for character codes greater than 127 is platform dependent.

ord[edit | edit source]

[Note: Requires version 2019.05]

Convert a character to a number representing the Unicode code point. If the parameter is not a string, the ord() returns undef.


Convert the first character of the given string to a Unicode code point.


// ECHO: 97

// ECHO: 66

echo([for (c = "Hello! 🙂") ord(c)]);
// ECHO: [72, 101, 108, 108, 111, 33, 32, 128578]

// ECHO: 1,"1" // only converts 1 character

len[edit | edit source]

returns the number of characters in a text.

echo(len("Hello world"));    // 11

Also See search()[edit | edit source]

search() for text searching.

is_string(value)[edit | edit source]

The function is_string(value) return true if the value is a string, false else

echo(is_string("alpha")); //true
echo(is_string(22)); //false

User defined functions[edit | edit source]

To complement native functions, you can define your own functions, some suggestions:

//-- Lower case all chars of a string -- does not work with accented characters
function strtolower (string) = 
  chr([for(s=string) let(c=ord(s)) c<91 && c>64 ?c+32:c]); 

//-- Replace char(not string) in a string  
function char_replace (s,old=" ",new="_") = 
  chr([for(i=[0:len(s)-1]) s[i]==old?ord(new):ord(s[i])]);

//-- Replace last chars of a string (can be used for file extension replacement of same length)
function str_rep_last (s,new=".txt") = 
  str(chr([for(i=[0 :len(s)-len(new)-1])ord(s[i])]),new);

//-- integer value from string ---------- 
//Parameters ret and i are for function internal use (recursion)
function strtoint (s, ret=0, i=0) =
  i >= len(s)
  ? ret
  : strtoint(s, ret*10 + ord(s[i]) - ord("0"), i+1);

Note here the use of chr() to recompose a string from unknown number of caracters defined by their ascii code. This avoid using recursive modules as was required before list management came in.