Methods to interpret string expressions. Source: 11.js, line 669 Methods concat() [ 'concat' a b ] returns String. Source: 11.js, line 673 input() [ 'input' prompt? default? ] returns String. Source: 11.js, line 683 len() [ 'len' b ] returns Number. Source: 11.js, line 690 string() [ 'string' value ] returns String. Source: 11.js, line 700