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// This file is part of www.nand2tetris.org
// and the book "The Elements of Computing Systems"
// by Nisan and Schocken, MIT Press.
// File name: projects/12/String.jack
/**
* Represents character strings. In addition for constructing and disposing
* strings, the class features methods for getting and setting individual
* characters of the string, for erasing the string's last character,
* for appending a character to the string's end, and more typical
* string-oriented operations.
*/
class String {
field int maxLen;
field int len;
field Array s;
/** constructs a new empty string with a maximum length of maxLength
* and initial length of 0. */
constructor String new(int maxLength) {
if (maxLength > 0) {
let s = Array.new(maxLength);
}
let maxLen = maxLength;
let len = 0;
return this;
}
/** Disposes this string. */
method void dispose() {
if (maxLen > 0) {
do s.dispose();
}
do Memory.deAlloc(this);
return;
}
/** Returns the current length of this string. */
method int length() {
return len;
}
/** Returns the character at the j-th location of this string. */
method char charAt(int j) {
if ((j < 0) | (j + 1 > len)){
do Output.printString("String.charAt: index out of range!");
do Sys.error(5);
}
return s[j];
}
/** Sets the character at the j-th location of this string to c. */
method void setCharAt(int j, char c) {
if ((j < 0) | (j + 1 > len)){
do Output.printString("String.setCharAt: index out of range!");
do Sys.error(5);
}
let s[j] = c;
return;
}
/** Appends c to this string's end and returns this string. */
method String appendChar(char c) {
if (len = maxLen) {
do Output.printString("String.appendChar: reached max length!");
do Sys.error(5);
}
let s[len] = c;
let len = len + 1;
return this;
}
/** Erases the last character from this string. */
method void eraseLastChar() {
if (len = 0){
do Output.printString("String.eraseLastChar: string is already empty!");
do Sys.error(5);
}
let len = len - 1;
return;
}
/** Returns the integer value of this string,
* until a non-digit character is detected. */
method int intValue() {
var int n, i;
var char c;
var boolean neg, done;
let n = 0;
if (s[0] = 45) {
let i = 1;
let neg = true;
} else {
let i = 0;
let neg = false;
}
let c = s[i];
if ((c < 48) | (c > 57)) {
do Sys.error(3);
do Output.printString("String.intValue: the input data is not number!");
}
let done = false;
while ((~done) & (i < len)) {
let c = s[i];
if ((c > 47) & (c < 58)) {
let n = n * 10 + (c - 48);
} else {
let done = true;
}
let i = i + 1;
}
if (neg) {
return -n;
} else {
return n;
}
}
/** Sets this string to hold a representation of the given value. */
method void setInt(int val) { //change Output.printInt after this
var int x, i, y;
var boolean neg;
if (val < 0) {
let neg = true;
let len = 2;
} else {
let neg = false;
let len = 1;
}
let x = Math.abs(val);
if (x > 9999) {
let len = len + 4;
} else { if (x > 999) {
let len = len + 3;
} else { if (x > 99) {
let len = len + 2;
} else { if (x > 9) {
let len = len + 1;
}}}}
if (len > maxLen) {
do Output.printString("String.setInt: val is too big for the string!");
do Sys.error(5);
}
if (x = 0) {
do setCharAt(0, 48);
return;
}
if (neg) {
do setCharAt(0, 45);
}
let i = len - 1;
while (x > 0) {
let y = x / 10;
do setCharAt(i, x - (y * 10) + 48);
let x = y;
let i = i - 1;
}
return;
}
/** Returns the new line character. */
function char newLine() {
return 128;
}
/** Returns the backspace character. */
function char backSpace() {
return 129;
}
/** Returns the double quote (") character. */
function char doubleQuote() {
return 34;
}
}
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