github.com/gopherd/gonum@v0.0.4/mathext/internal/amos/amoslib/zexp.f (about)

     1        SUBROUTINE ZEXP(AR, AI, BR, BI)
     2  C***BEGIN PROLOGUE  ZEXP
     3  C***REFER TO  ZBESH,ZBESI,ZBESJ,ZBESK,ZBESY,ZAIRY,ZBIRY
     4  C
     5  C     DOUBLE PRECISION COMPLEX EXPONENTIAL FUNCTION B=EXP(A)
     6  C
     7  C***ROUTINES CALLED  (NONE)
     8  C***END PROLOGUE  ZEXP
     9        DOUBLE PRECISION AR, AI, BR, BI, ZM, CA, CB
    10        ZM = DEXP(AR)
    11        CA = ZM*DCOS(AI)
    12        CB = ZM*DSIN(AI)
    13        BR = CA
    14        BI = CB
    15        RETURN
    16        END