Naming Conventions
	Scalar	Vector	Matrix	Any rank	Non- scalar
Boolean	`BS`	`BV`	`BM`	`BA`	`BN`
Integer	`IS`	`IV`	`IM`	`IA`	`IN`
Float	`FS`	`FV`	`FM`	`FA`	`FN`
Numeric	`NS`	`NV`	`NM`	`NA`	`NN`
Character	`CS`	`CV`	`CM`	`CA`	`CN`
Enclosed vector	`ES`	`EV`	`EM`	`EA`	`EN`
enclosed Text vector	`TS`	`TV`	`TM`	`TA`	`TN`
Simple	`SS`	`SV`	`SM`	`SA`	`SN`
Any	`AS`	`AV`	`AM`	`AA`	`AN`
phrase e.g.: `.X...Y. ⍝ X←BS; Y←IV`
combinations: use `ISV` for Integer scalar`∨`vector
`B3`, `I4` &c. to specify higher ranks.

DeleteLeadingBlanks

The task to delete leading blanks from a string is a very common one. APL dialects might provide a utility function for this. Common names are rlb (remove leading blanks) and dlb (delete leading blanks).

There are a couple of approaches available but one which is supposed to run in almost all flavours of APL is this one:

      (+/∧\' '=CV)↓CV

Examples

      ⎕FX ⊃'r←dlb cv' 'r←(+/∧\'' ''=cv)↓cv'
      '|',( dlb'    hello world   '),'|'
|hello world   |

Specialities

Dyalog

This dfn (direct function):

      {(+/∧\' '=⍵)↓⍵}

is recognized in Dyalog as an Idiom and therefore recognized as such and executed faster than the ordinary APL expression.

Compatibility

CheckedWith: APL2, APLX, Dyalog, NARS2000

Test Cases

Show Hide test cases test cases

Test
 ⎕IO←0      ⍝ You may change this; however, zero IS the default in the Phrasebook
⍝⎕ML←3      ⍝ Enable this line in Dyalog APL if appropriate
  ⎕FX ⊃'r←dlb cv' 'r←(+/∧\'' ''=cv)↓cv'
⍝ ---- Start Test cases (do not delete this!)
 ''≡dlb''
 ''≡dlb' '
 'APL'≡dlb' APL'
 'APL is great'≡dlb'  APL is great'
 'APL is great   '≡dlb'  APL is great   '

For details see the PhraseBook/TestCasesGuidelines.

Test my code, both Examples and Test Cases.

Mentor: KaiJaeger

Tags: <Blanks> <DeleteBlanks> <RemoveBlanks>