J3/06-114r2 Date: 16 Feb 2006 Subject: ATAN with two arguments works like ATAN2 From: /jor/Stan Whitlock References: J3-026 Revised Suggested edits (cf 06-114) [294:27] After "ATAN(X)" add "or ATAN(Y,X)" [298:16+15] After "ATAN" in the first column in the table in 13.6, insert "(X)". [305:28] After "ATAN(X)" add " or ATAN(Y,X)" [305:31-34] Change to read: Arguments. Y shall be of type real. X If Y is present, X shall be of type real with the same kind type parameter as Y. If Y has the value zero, X shall not have the value zero. If Y is absent, X shall be of type real or complex. Result characteristics. Same as X. Result value. If Y is present, the result is the same as the result of ATAN2(Y,X). If Y is absent and X is real, the result is real, is expressed in radians, and has a value equal to a processor-dependent approximation to arctan(X) that lies in the range $-\frac\pi2 \leq$ ATAN(X) $\leq \frac\pi2$. If Y is absent and X is complex, the result is complex. The real part is expressed in radians and lies in the range $-\frac\pi2 \leq$ REAL(ATAN(X)) $\leq \frac\pi2$. Note 1 to editor: please add a note on page xiii: xx) The ATAN intrinsic is extended so that ATAN (Y, X) is ATAN2 (y,X). Note 2 to editor: these edits assume that paper 05-204r2 has passed. If 05-204r2 is withdrawn, the text in "Arguments." X If Y is present, X shall be of type real with the same kind type parameter as Y. If Y has the value zero, X shall not have the value zero. If Y is absent, X shall be of type real or complex. becomes X shall be of type real. If Y is present, X shall have the same kind type parameter as Y. If Y has the value zero, X shall not have the value zero. and the text in "Result value." If Y is absent and X is real, the result is real, is expressed in radians, and has a value equal to a processor-dependent approximation to arctan(X) that lies in the range $-\frac\pi2 \leq$ ATAN(X) $\leq \frac\pi2$. If Y is absent and X is complex, the result is complex. The real part is expressed in radians and lies in the range $-\frac\pi2 \leq$ REAL(ATAN(X)) $\leq \frac\pi2$. becomes If Y is absent, the result is real, is expressed in radians, and has a value equal to a processor-dependent approximation to arctan(X) that lies in the range $-\frac\pi2 \leq$ ATAN(X) $\leq \frac\pi2$. Note to text users: "$-\frac\pi2 \leq$ ATAN(X) $\leq \frac\pi2$" is fancy way of saying "-pi/2 <= ATAN(X) <= pi/2".