slicearrayi

Copies selected array elements at initialization only.

Use slicearrayi to select notes from a scale or keep a copy of settings from a global array when an instrument starts. The spelling slicearray_i calls the same opcode.

Syntax

ModernClassic

iout[] = slicearrayi(iin[], istart, iend [, istride])
kout[] = slicearrayi(kin[], istart, iend [, istride])
Sout[] = slicearrayi(Sin[], istart, iend [, istride])

iout[] slicearrayi iin[], istart, iend [, istride]
kout[] slicearrayi kin[], istart, iend [, istride]
Sout[] slicearrayi Sin[], istart, iend [, istride]

Use slicearray_i in place of slicearrayi for the older spelling. It accepts the same arguments and types.

Initialization

The input must be an initialized, one-dimensional array. Supported element types are i-rate numbers, k-rate numbers and strings. The output has the same element type as the input. Audio arrays and arrays of other types have no slicearrayi form.

istart is the first input index to copy. Indices start at 0.

iend is the last input index allowed in the slice, inclusive. Use -1 to select through the last input element. This argument is required, including when selecting to the end.

istride is the step between input indices. It defaults to 1. A stride of 2 copies every other element, starting at istart.

The opcode sizes the output to hold the selected elements. You do not need to declare its size first. For example, slicing [10, 20, 30, 40, 50, 60] from 1 through 4 with a stride of 2 returns [20, 40]. The end element is copied only if a step reaches it.

The copy runs during initialization, including reinitialization. It does not run on control cycles, even with a k-rate or string array. Later changes to the input leave the output unchanged. Strings are copied too, so changing a source string does not change its copy.

For k-rate inputs, set the values before the slice runs. A global array filled before the instrument starts is one use for this form. A value first assigned during performance is not yet available at initialization. Use slicearray when the slice should follow changes during performance.

Bounds and stride

Use integer indices and a positive integer stride. Fractional arguments truncate toward zero after the range checks. An end value whose integer part is negative selects the last input element.

The start must be between 0 and the input length. An end index beyond the last element causes an initialization error. A start beyond the selected end returns an empty array, so a start equal to the input length also returns an empty array.

All arguments must be finite. The stride must be at least 1 and less than 2147483648. The end must be at least -2147483648 and less than 2147483648. Invalid bounds, a stride outside its range or an input with more than one dimension cause an initialization error.

Examples

The example selects the first, third and fifth notes of a major scale to make a chord. The scale lives in a global k-rate array. Each note takes its own copy at initialization.

A matching string slice supplies the note names. The example prints C E G and plays the chord for two seconds.

It uses slicearrayi.csd.

Choose a chord from a scale at note start
<CsoundSynthesizer>
<CsOptions>
-d -o dac
</CsOptions>
<CsInstruments>
sr = 48000
ksmps = 32
nchnls = 1
0dbfs = 1

// Fill the scale before any instrument starts.
gkScale[] fillarray 60, 62, 64, 65, 67, 69, 71

instr Chord
  // Include indices 0, 2 and 4. The end index is inclusive.
  kNotes[] = slicearrayi(gkScale, 0, 4, 2)
  SNames[] fillarray "C", "D", "E", "F", "G", "A", "B"
  SChord[] = slicearrayi(SNames, 0, 4, 2)
  prints "%s %s %s\n", SChord[0], SChord[1], SChord[2]

  // These notes keep the scale values copied when the instrument started.
  kRoot = cpsmidinn(kNotes[0])
  kThird = cpsmidinn(kNotes[1])
  kFifth = cpsmidinn(kNotes[2])
  aRoot = oscili(0.15, kRoot)
  aThird = oscili(0.15, kThird)
  aFifth = oscili(0.15, kFifth)
  aEnvelope = linen(1, 0.02, p3, 0.1)
  out((aRoot + aThird + aFifth) * aEnvelope)
endin
</CsInstruments>
<CsScore>
i "Chord" 0 2
e
</CsScore>
</CsoundSynthesizer>

Credits

Author John ffitch, 2018.

The original spelling slicearray_i appeared in Csound 6.12. The spelling slicearrayi is available in Csound 7.