Built-in functions from the insert

A receipt joins a number to text

• Every Paper 2 has an insert of built-in functions. Anything not in the pseudocode guide is printed there, and an answer may call it.
• LEFT(Text, N) copies the first N characters. Positions still start at 1.
• NUM_TO_STR(87.5) is the string "87.5". Join it with & when the line must contain words and a number.

OUTPUT LEFT("Computer", 3)
OUTPUT "Score: " & NUM_TO_STR(87.5)

Check before you convert

• IS_NUM(Text) is TRUE only when the string is a number. "12a" is FALSE.
• STR_TO_NUM("23") is the number 23, so you can add 1 to it. A string cannot be added.
• Convert only after IS_NUM says the text is safe.

DECLARE Text : STRING
Text ← "23"
IF IS_NUM(Text) THEN
    OUTPUT STR_TO_NUM(Text) + 1
ELSE
    OUTPUT "bad"
ENDIF

ASC and CHR

• ASC("A") is the integer code 65. CHR(66) is the character "B".
• The next letter after "A" is CHR(ASC("A") + 1).

OUTPUT CHR(ASC("A") + 1)
OUTPUT IS_NUM("12a")

Common mistakes

• UCASE still takes one character. A whole string in capitals is TO_UPPER, which you met earlier.
• NUM_TO_STR returns text. STR_TO_NUM returns a number. They are not interchangeable.

Now you try

• Use LEFT, then a joined number, then IS_NUM before a conversion.