International
Tables for
Crystallography
Volume G
Definition and exchange of crystallographic data
Edited by S. R. Hall and B. McMahon

International Tables for Crystallography (2006). Vol. G, ch. 2.4, pp. 45-46

Section 2.4.4.2. Looped lists

F. H. Allen,a* J. M. Barnard,b A. P. F. Cookb and S. R. Hallc

aCambridge Crystallographic Data Centre, 12 Union Road, Cambridge, CB2 1EZ, England,bBCI Ltd, 46 Uppergate Road, Stannington, Sheffield S6 6BX, England, and cSchool of Biomedical and Chemical Sciences, University of Western Australia, Crawley, Perth, WA 6009, Australia
Correspondence e-mail:  allen@ccdc.cam.ac.uk

2.4.4.2. Looped lists

| top | pdf |

Repetitive data are stored in a MIF as lists of values, as they are in a CIF. Each list is prefaced by a loop_ statement and a sequence of data names that identify the data values that follow in `packets' of equal length. The values in each packet match the order and number of the data names. Any number of packets may appear in a looped list.

Atom and bond properties are typical of the information to appear in a looped list. The atoms and bonds of thiabutyrolactone in MIF format are shown in Fig. 2.4.4.1[link]. The description of each data item in this example is given in Chapter 4.8[link] , although the meanings are clear from the self-descriptive data names. The number of data values in each list is an exact multiple of the number of data names at the start of each loop structure. Looped lists are terminated by the next list or by any other data name, data block or end of file. Comments may be included in a MIF and are preceded by a # character, as illustrated in Fig. 2.4.4.1[link].

[Figure 2.4.4.1]

Figure 2.4.4.1 | top | pdf |

MIF coding of atom and bond properties for thiabutyrolactone.

Hierarchical data may require the use of nested loop structures (see the _display_* loop in Fig. 2.4.4.2[link]). Note that the packet for _display_id of 7 has two sets of _display_conn_ values giving connections to atom sites 1 and 4 (the other connections to site 7 appear in the next two packets). Data items that appear in looped lists are identified in the MIF dictionary (see Chapter 4.8[link] ) as having the attribute _list set to either `yes' or `both'. Other relationships between looped data items are also specified in the dictionary.

[Figure 2.4.4.2]

Figure 2.4.4.2 | top | pdf |

MIF coding of atom properties (including 3D coordinates), bond properties and display information for (+)-3-bromocamphor.








































to end of page
to top of page