if

Name

if --  Branches conditionally at initialization or during performance time.

Description

if...igoto -- conditional branch at initialization time, depending on the truth value of the logical expression ia R ib. The branch is taken only if the result is true.

if...kgoto -- conditional branch during performance time, depending on the truth value of the logical expression ka R kb. The branch is taken only if the result is true.

if...goto -- combination of the above. Condition tested on every pass.

if...then -- synthesizes internal labels allowing the ability to specify "if/else/endif" blocks as some traditional programming languages do. Any block that begins with an "if...then" statement must end with an endif statement. elseif and else statements are optional. Any number of elseif statements are allowed. Only one else statement may occur and it must be the last conditional statement before the endif statement. Nested "if...then" statements are allowed.

Note: Note that if the condition uses a k-rate variable (for instance, "if kval > 0"), the if-test and the goto will be ignored during the i-time pass, even if the k-rate variable has already been assigned an appropriate value by an earlier init statement.

Syntax

if ia R ib igoto label
if ka R kb kgoto label
if ia R ib goto label
if xa R xb then

where label is in the same instrument block and is not an expression, and where R is one of the Relational operators (<, =, <=, ==, !=) (and = for convenience, see also under Conditional Values).

Examples

Here is an example of the if...igoto combination. It uses the files igoto.orc and igoto.sco.

Example 15-1. Example of the if...igoto combination.

/* igoto.orc */
; Initialize the global variables.
sr = 44100
kr = 4410
ksmps = 10
nchnls = 1

; Instrument #1.
instr 1
  ; Get the value of the 4th p-field from the score.
  iparam = p4

  ; If iparam is 1 then play the high note.
  ; If not then play the low note.
  if (iparam == 1) igoto highnote
    igoto lownote

highnote:
  ifreq = 880
  goto playit

lownote:
  ifreq = 440
  goto playit

playit:
  ; Print the values of iparam and ifreq.
  print iparam
  print ifreq

  a1 oscil 10000, ifreq, 1
  out a1
endin
/* igoto.orc */
        
/* igoto.sco */
; Table #1: a simple sine wave.
f 1 0 32768 10 1

; p4: 1 = high note, anything else = low note
; Play Instrument #1 for one second, a low note.
i 1 0 1 0
; Play a Instrument #1 for one second, a high note.
i 1 1 1 1
e
/* igoto.sco */
        
Its output should include lines like this:
instr 1:  iparam = 0.000
instr 1:  ifreq = 440.000
instr 1:  iparam = 1.000
instr 1:  ifreq = 880.000
      

Here is an example of the if...kgoto combination. It uses the files kgoto.orc and kgoto.sco.

Example 15-2. Example of the if...kgoto combination.

/* kgoto.orc */
; Initialize the global variables.
sr = 44100
kr = 4410
ksmps = 10
nchnls = 1

; Instrument #1.
instr 1
  ; Change kval linearly from 0 to 2 over
  ; the period set by the third p-field.
  kval line 0, p3, 2

  ; If kval is greater than or equal to 1 then play the high note.
  ; If not then play the low note.
  if (kval >= 1) kgoto highnote
    kgoto lownote

highnote:
  kfreq = 880
  goto playit

lownote:
  kfreq = 440
  goto playit

playit:
  ; Print the values of kval and kfreq.
  printks "kval = %f, kfreq = %f\\n", 1, kval, kfreq

  a1 oscil 10000, kfreq, 1
  out a1
endin
/* kgoto.orc */
        
/* kgoto.sco */
; Table #1: a simple sine wave.
f 1 0 32768 10 1

; Play Instrument #1 for two seconds.
i 1 0 2
e
/* kgoto.sco */
        
Its output should include lines like this:
kval = 0.000000, kfreq = 440.000000
kval = 0.999732, kfreq = 440.000000
kval = 1.999639, kfreq = 880.000000
      

Examples

Here is an example of the if...then combo. It uses the files ifthen.orc and ifthen.sco.

Example 15-3. Example of the if...then combo.

/* ifthen.orc */
sr = 44100
kr = 4410
ksmps = 10
nchnls = 1

; Instrument #1.
instr 1
  ; Get the note value from the fourth p-field.
  knote = p4

  ; Does the user want a low note?
  if (knote == 0) then
    kcps = 220
  ; Does the user want a middle note?
  elseif (knote == 1) then
    kcps = 440
  ; Does the user want a high note?
  elseif (knote == 2) then
    kcps = 880
  endif

  ; Create the note.
  kamp init 25000
  ifn = 1
  a1 oscili kamp, kcps, ifn

  out a1
endin
/* ifthen.orc */
        
/* ifthen.sco */
; Table #1, a sine wave.
f 1 0 16384 10 1

; p4: 0=low note, 1=middle note, 2=high note.
; Play Instrument #1 for one second, low note.
i 1 0 1 0
; Play Instrument #1 for one second, middle note.
i 1 1 1 1
; Play Instrument #1 for one second, high note.
i 1 2 1 2
e
/* ifthen.sco */
        

See Also

elseif, else, endif, goto, igoto, kgoto, tigoto, timout

Credits

Examples written by Kevin Conder.

Added a note by Jim Aikin.